In a broad sense, three-dimensional (“3-D”) scanning involves using a machine to capture or record the shape of an object in three dimensions, typically for purposes of forming a 3-D representation of the object (e.g., a stereoscopic picture or computer-aided design (CAD) model). As such, 3-D scanning has many uses, including: computer vision, visualization methods, and/or “virtual reality,” e.g., with 3-D monitors and goggles; parts inspection; modeling; security scans; manufacturing; and stereolithography.
Over the years, various devices have been developed for 3-D scanning, many of which are necessarily quite sophisticated. For example, one commercially-available system (see www.3dscanners.com) uses a laser and camera system for laser stripe triangulation. This involves moving a laser line across the object, which is then viewed by an off-angle camera such that height/size variations in the object are seen as changes in line shape. Another system (see www.rolanddga.com) utilizes direct contact, where an array of piezoelectric sensors (flexible elements whose output voltage is proportional to the mechanical pressure applied to them) is dragged across the object.
While these systems generally work well, they can be quite expensive, and are therefore unattractive to consumers, businesses, and other organizations who have limited budgets or who only need occasional 3-D scanning capability. Accordingly, developers have sought to use more widely available (and less expensive) scanners, e.g., flatbed optical scanners or photocopiers, to achieve similar results.
Flat-bed, optical (light-based) scanners are used to copy two-dimensional documents and to transfer documents to computer. For example, in the case of a traditional photocopier, light is sequentially applied to portions of a document, which reflects off the document and onto the surface of a charged photoreceptive drum. Toner (charge-sensitive “ink”) is attracted to the drum in areas where light did not hit the drum, resulting in a toner pattern that corresponds to the pattern of dark (e.g., text) on the document. The toner is subsequently transferred to a blank sheet of paper, resulting in a copy of the document. In the case of computer scanners, light is also “bounced off” a document, but instead of being applied to a photoreceptive drum, it is applied to a CCD (charge-coupled device) array or other appropriate type of sensor, either directly or via a series of mirrors and lens. The CCD array converts the light into electrical charges which can be read by the computer and converted into an image of the scanned document.
FIGS. 1A and 1B show existing scanners. There, an object 20 is placed on the scanner's flat glass plate 22. In the case of a “moving sensor”-type scanner 24 (FIG. 1A), a carriage or head 26 has an optic axis 27 (here, vertically-oriented), and a CCD array or other sensor 28. For scanning, the carriage 26 is moved under the object 20. The sensor 28 detects light reflecting straight down off the object 20 through the glass 22, either directly or via a mirror/lens system also attached to the carriage. In the case of a “moving mirror”-type scanner 30 (FIG. 1B), the sensor 28 is stationary, and light is directed from the object to the sensor via an appropriately-angled, rectangular mirror 32, which is attached to the moving head or carriage 26.
While existing copiers and scanners work very well with two-dimensional documents, they are not capable of creating 3-D representations of objects by themselves. More specifically, to the extent copiers and scanners can be used to scan objects, the result is simply a flat, single-orientation picture of the object, without any true sense of the object in three dimensions. Moreover, light from portions of the object away from the scanner's or copier's flat glass plate is oftentimes not received by the CCD array or photoreceptive drum, resulting in dark or “muddy” pictures. However, it is possible to convert, adapt, and/or otherwise utilize conventional flatbed optical scanners and scanning technology to capture 3-D images.
One such system (see www.stereoscopicscanning.de) involves taking two scans of a generally-flat (but still three-dimensional) object. For the first scan, the object is positioned on the right side of the scanning path, and for the second scan, the object is positioned on the left side of the scanning path. As should be appreciated, this results in two flat pictures of the object at different orientations, which can be converted into a stereoscopic image. Additionally, multiple scans of the object can be taken, with the object being successively moved laterally (with respect to the path of the scanning element), for each scan. The successive string of pictures, each of the object at a slightly different orientation, can be displayed sequentially to produce an illusion of the object rotating in three dimensions, like a flip book or cartoon. However, while this system produces some interesting results, it is disadvantageous because the object itself has to be moved, requiring either manual input or a separate movement mechanism. Furthermore, it is quite difficult to convert the images into accurate computer form because of left-to-right light divergence and because the relationship of the lateral angle of the object with respect to the scanner/CCD array is unknown and/or difficult to measure with accuracy.
Accordingly, a primary object of the present invention is to provide an inexpensive and easily-constructed flatbed optical scanner capable of obtaining an accurate model or other representation, in three dimensions, of a non-flat object.